In this paper, the diffraction of Rayleigh waves around a circular cavity in poroelastic half-space was investigated by indirect boundary integral equation method based on the Biot’s two-phase medium theory. The impacts of incident wave frequencies, porosities, drainage boundary conditions and depths of cavity on the displacement and pore pressure responses were discussed in detail. The results show that the existence of circular cavity amplifies the surface displacement and pore pressure in poroelastic half-space. The peak values of horizontal and vertical surface displacement were enlarged by 10.1 times and 11.2 times respectively for drained boundary, and enlarged by 12.0 times and 9.6 times respectively for undrained boundary. The peak value of surface pore pressure increases by 2.1 to 3.0 times compared with the free field responses. The peak values of displacement and pore pressure responses were both found at the cavity boundary close to the incident wave. With the increase of incident wave frequency or cavity depth, the amplification effect was weakened. The maximum pore pressure around cavity was found at the top of the cavity. For constant porosity, the pore pressure around cavity will reach the highest level when the incident frequency is 1.0 and reach the lowest level when the incident frequency is 2.0.